Battery type for Phoenix Brute - Nimh, LifePo4?

I'm a big guy...350. I put a Brute kit on a Worksman bike last year and I love it but...

I want to ride this to work. It's 20 miles RT. I can charge the bike at work.
Currently I have 48V 12ah SLA (two 24v 12ah in series)

The first day I rode to work the batteries gave out about a mile from work. I was able to make it but it was a scare and I want to be sure I have the power available.
On the ride home I pedal more because I don't mind if I sweat. The ride home I pedaled a lot more and the battery indicator turned yellow but did not cut out.

I want enough battery power to make it one way (in the morning when I don't pedal very much) and welcome advice selecting different battery technology.

I got the kit from Electric Rider and they only recommend SLA batteries. They do have a company on their site that sells Nimh batteries but don't really recommend them, but, if you're going to use Nimh that's who they would use.

I've heard/read that LifePo4 batteries may not be able to supply high current for long periods. I've heard that Nimh are sensitive to discharge/charge cycles...

I don't want to change the motor to a higher voltage unless absolutely necessary.

Is the info I've been reading old info?
Should I get Nimh or LifePo4?
Do you think 48v 20ah would be sufficient using either battery type or would 30ah be best?

I think it's clear that 20ah is your minimum required pack size. Another consideration is the amps/watts required by your motor/controller.

Yeah, Electric Rider's website does go on about not finding any battery that lives up to their testing.

Do you have any idea what the amps used with your setup is? e.g. what's the amps rating of the controller? I think it's a 35A controller?

The battery pack will have a rating on A's it can provide. Be careful on that rating. e.g. A few years ago I got a NiMH pack made from D cells and didn't read the rating and learned the hard way that a 35A controller drawing power from a NiMH pack rated for 10A max makes the batteries very hot.

Typically battery ratings are for long period discharge. It's definitely not a good idea to make a sweeping generalization like "LifePo4 batteries may not be able to supply high current for long periods". I've not heard such a thing and have seen LiFePO4 used in vehicles both small and large. There may be specific manufacturers whose cells cannot supply high current for long periods, but that doesn't seem to be a generally true statement. For example in high speed electric motorcycles there is experience with LiFePO4 giving high speed for the length of time required for a road race around the Isle of Man covering a 38 mile distance and climbing a 1400 foot mountain.

The motor is: Crystalyte Phoenix Brute X-5305, 48v, front wheel mount (1920 watts)
The controller is: Their 4840 controller...I think the 4840 stands for 48v, 40a
The batteries are: new 12v, 12ah, quantity 4 wired in series for 48v, 12ah.
The wiring was their harness that came with the kit, pre-wired.
The charger came with the kit and I have no reason to question it's size. It seems to charge the batteries just fine.

The kit is good. I am very pleased with the torque and power with me being 350 lbs. I just need more range.

I assume from your reply that you would have no problem using LifePO4 batteries on this setup. What size would you think about using?...48v, 20ah batteries, two of them wired in parallel? I assume a larger controller would be required??? If I get a larger controller, I'm going to get one with an analyzer readout screen.

Thanks again for all the help, I've been reading the forums here for awhile and would like your input.

One of these days I'm going to put two kits on a bike, a front wheel motor and a rear wheel motor and maybe an Aevon type trailer to pull the batteries...
:-) DT98

You should get greatest range, and longer "Run Time" by operating the 2 batteries in parallel, this is because the effective discharge RATE will be cut in half, with much less power wasted in heating the battery due to internal battery resistance. Best parallel operation is with IDENTICAL batteries!--Good luck,---- Bob.